Within the past 25 years, automobile design has changed substantially. Integration of emerging technologies and software in vehicle design have led to dramatic improvements in fuel efficiency, emission reduction, and driver experiences. One of these emerging technologies is the Electronic Throttle Control
(ETC). Spark ignition engines have traditionally, and for the most part continue to be, throttle governed. Throttle governing refers to the control of an engine's power output and/or speed through the manipulation of the amount of air allowed to enter the engine's intake manifold via a throttle body assembly. When the throttle is opened a small amount, only a small amount of air can enter the engine. This lowers the amount of power the engine can produce and minimizes the speed at which the engine can operate. When the throttle is opened further, more air enters the engine, increasing power output and engine speed. This manipulation of the throttle and airflow into the engine is affecting the engine's volumetric efficiency. By changing the engine's volumetric efficiency, the driver can increase or decrease the power output of the engine and ultimately the speed of the vehicle.
Before the advent of ETC, traditional vehicles were outfitted with a throttle cable or throttle linkage rod. These systems placed a mechanical link between the throttle body and the accelerator pedal. When the driver depressed the accelerator pedal, the throttle cable or linkage rod directly opened the throttle body and increased the engine's volumetric efficiency. This system was functional, but ETC systems have many benefits over the traditional mechanical linkage; improved vehicle drivability, throttle response, and fuel economy are expected from precise throttle manipulation. Integration of throttle control with adaptive cruise control, traction control, idle speed control, and vehicle stability control is now possible, leading to increased synergy between vehicle systems. Optimization of air supply will ensure harmful exhaust emissions are kept to a minimum.